Fructan is a polydisperse fructose polymer. Biosynthesis of fructan uses sucrose as the starter molecule to which fructosyl units, obtained from sucrose, are added during the elongation process. Bacterial fructan typically has a very high degree of polymerization (DP) which can reach as many as 100,000 fructose units. In plants, the DP generally does not exceed 100.
Fructan with β(2-1) glycosidic linkages is called inulin. Inulin can result from the elongation of the fructan chain starting from the C1 of the fructose moiety of the initial sucrose. Alternatively, inulin can result from the elongation form the C1 of the fructose moiety as well as from the C6 of the glucose moiety of the starter sucrose.
Fructan with β(2-6) glycosidic linkages is called levan and is produced by bacteria and grasses. Fructan consisting of fructose molecules with two types of linkages is called graminan and mixed levan. The mixed glycosidic linkages results in branched fructan molecules. Branched fructans are found in oats and several other members of the Graminae.
Within the plant kingdom, about 45,000 species, accounting for about 15% of the flowering plants, accumulate fructan as a storage carbohydrate. In these plants, inulin is produced in addition to, or instead of, starch.
Fructan is not digested in the upper part of the human digestive track. The β(2-1) and β(2-6) linkages in fructan are not cleaved by human digestive enzymes involved in starch and sucrose degradation such as maltase, sucrose, isomaltase or β-glucosidase. As a result, approximately 85% of the ingested fructan reaches the colon where it is fermented by beneficial endogenous microflora. The main fermentation products are short chain fatty acids.
Inulin increases the volume of microbial biomass in the colon. With each gram of ingested inulin increases the fecal wet weight by 1.5 to 2 grams.
Increased consumption of fermentable carbohydrate such as the natural chicory fiber inulin results in reduced weight gain and consumption of less food.
Inulin is a reserve carbohydrate in stems and taproots of chicory (Cichorium intybus L.) plants. However, the bitterness of the taproots limits their consumption. Presently, the removal of the bitter taste is a costly step in the production of inulin from chicory roots, which makes chicory fibers significantly more expensive than cellulose fibers. Hence, there is a need in the art for an economic process for producing low bitter chicory products (e.g., inulin-containing flour or dough) that avoids the costly steps of inulin extraction from the taproot and the separation thereof from bitter compounds.